5 Best Weed Killers For St. Augustine Grass

Florida, the Carolinas, and Southern California are the U.S. states where you can find St. Augustine weed growing on your lawn. This turfgrass makes a thick green lawn in warm coastal areas. But without proper maintenance (fertilization is a must-do thing) this grass/weed can quickly become a problem for any homeowner.

There are some remedies capable of fertilizing and at the same time controlling the growth of St. Augustine. Check the best multi-purpose weed killers that you may use for controlling St. Augustine.

Southern Ag Surfactant for Herbicides – the best for killing St. Augustine weeds with herbicides!

This surfactant stands for 80% non-ionic wetting agent. It improves the action of any herbicide providing its better penetration and coverage. Southern Ag Surfactant is compatible practically with any herbicide brand that comes to mind – Trimec, Atrazine, Brush Killer, to name the few.

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Tips for users: 1 teaspoonful of this product is usually enough to boost 1 gallon of any herbicide (you may need a higher dosage for boosting Round-up and MSMA) – but check the label directions before mixing two products.

Pros

Pros

• It will work not only with broadleaf and turfgrass weeds but also with poison ivy, sumac, Bermuda, horsetail
• More effective than liquid (dish) soap for improving herbicides
• Compatible with most herbicides and fertilizers (try mixing it with blue dye)
• Compatible with hose-end sprayers
• Efficient use
• Quick action

Cons

Cons

• Be careful! It may kill flowers and herbs if used improperly
• Check the label instructions – if you take too much of this product, it will just act as a fertilizer
• Won’t kill all weed types
• Some users think that its price is high

This product is good only for mixing with herbicides to kill weeds. Never apply just this remedy – it won’t work. It is recommended only for improving the effectiveness of your regular herbicide.

The Andersons Pro Weed Killer – the best pre-emergent product for St. Augustine weeds!

A powerful turf granular weed killer of the pre-emergent method of action. It acts as an efficient spot weed killer. It is fully compatible with the edge spreader (the settings are 4 – 7.5).

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The Anderson Pro product can be spread all over the garden area including rock gardens and the areas under the trees. It is enough to treat the lawn with it twice per year – in the spring and fall.

Pros

Pros

• One of the best pre-emergent treatments for killing broadleaf weeds
• Easy instructions to follow
• May act as a great spot weed killer

Cons

Cons

• May not work in some regions – uses claim that it may work in Georgia, but won’t affect in West Texas
• Pricey
• Won’t work in late winter or late autumn

This product may not work if applied in too cold or too hot weather – the best temperature for applying is around 500F. Use this treatment only twice per year and you won’t have any summer weeds.

Hi-Yield Atrazine Weed Killer – the best for killing almost any weeds anytime!

Voluntary Purchasing Group manufactured the product – Hi-Yield Atrazine weed killer – for destroying St. Augustine and similar weeds. It is based on a very effective component – 4% atrazine.

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One of the best properties of this product is high concentration – use ½ cup (1 oz) per gallon.

Pros

Pros

• The concentrated product
• Easy to apply
• The coverage area is 3720 square inches
• Compatible with hose-end sprayers
• Won’t harm vegetables and fruits
• Good for spot weed control as well

Cons

Cons

• Apply carefully, according to the directions – otherwise, you will destroy all grass in your backyard
• The shelf life is not long – about a few months
• You must invest in nutrients and fertilizers after applying this product

It will take from 2 to 4 weeks to see the result after the application. At first, the weeds turn yellow and only then dry. Test it on a small area before covering the whole lawn – it may not work in some regions or may kill good grass as well.

Southern Ag Atrazine – the best post-emergent weed killer for broadleaf and grassy weeds!

Southern AG weed killer is another powerful 4% atrazine remedy for controlling St. Augustine and centipede grass. For covering about 500 square feet it is enough to use 4.33 ounces per 1 gallon of spray (take 2 gallons of water and about 9 ounces of the product to cover 1,000 sq. ft.).

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Tips for users: Do not use this product as a pre-emergent weed treatment – only for post-emergent action, though Atrazine in other remedies is usually good for both effects. Do not apply while the grass is dormant. Never spread on sweet corn. It is good for applying when the temperature range is around 500F – mostly, in early spring. Do not irrigate for 72 hours after the application.

Pros

Pros

• It is efficient and cost-effective
• Good for controlling emerged weeds and weeds from seeds
• Large coverage area – 60,000 sq. ft.
• Besides lawn, you may use it for killing weeds on ditch banks, golf courses, parks and along fences

Cons

Cons

• Not compatible with hose-end sprayers – instead use a pump sprayer
• Won’t kill Spurweed or Poa Annua weed
• Do not let your pets swallow this product – it is extremely toxic
• May cause harm to turf, flowers, veggies, and fruits

It is better to use this product in early spring. The first results will be evident in 2 weeks. Sometimes you may need to apply the double dosage to achieve the best effect. In addition, it won’t be helpful if the product is applied with a surfactant.

PBI/Gordon Speed Zone Weed Killer – the best for large property owners!

This weed killer delivers fast results on large properties like backyards, parks, farms. It is a pre-emergent product that effectively kills even emerged weed types. One of the best remedies for the fast killing of St. Augustine weed – the results become visible in a few days, if not hours.

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Pros

Pros

• Highly concentrated
• Won’t harm any turfgrass or lawn grasses
• Visible results may appear in a few hours
• Cost-effective
• One gallon may destroy the weeds on the large area – up to 18,000 sq. ft.

Cons

Cons

• The manufacturer doesn’t ship this product to DC, NJ, VT, MA, and AK
• The package may leak

This product won’t work in dry and hot weather. It is better to apply this weed killer when the temperature range outside is about 50-600F. The speed of action is only a few hours, sometimes 1-2 days.

The Buyer’s Guide

Pre-emergent or post-emergent?

Before applying any new product on your lawn to get rid of St. Augustine, make a plan. At first, you should choose between post-emergent and pre-emergent remedies:

• Pre-emergent concoctions prevent weeds from growing;
• Post-emergent remedies attack fully grown weeds;

Most users and tests of scientists prove that pre-emergent products are more effective for killing St. Augustine weeds. It is better to apply such remedies when the weather is dry and the daytime temperature is about 65-750F – February or March for the first time and September for the second time per year.

Read the label before buying or applying!

However, not all pre-emergent remedies are good for killing this particular weed type. Read the label directions and instructions – most products have the limits pointed out by manufacturers. Some products are good for broadleaf weeds only, the others work for creeping grass types.

Check the components

Most herbicides that contain 2,4-dichlorophenoxyacetic acid and Atrazine will destroy St. Augustine weed. Other components are not very effective.

Video Tutorial: How to Remove Weeds from St. Augustine Grass

Final Thoughts

St. Augustine weed is not that hard to destroy. Use any of the above-mentioned remedies, according to the label direction. If you are not sure of the results, test a new herbicide on the small area free from good crops, flowers, vegetables, and fruits. The effect will become visible in a few days.